It’s been a record-breaking summer so far, with early-season heat waves pushing temperatures along the typically seasonable Northeast into the upper 90s and past 100. Those of us who are fans of hot yoga— whether we’re talking about mildly heated vinyasa or Bikram, where the room is set to a sweaty 105 degrees F—know that the practice can be a welcome relief in the cold winter months. But what about when temperatures outside the studio are hotter than temperatures in?

Whether induced by vigorous exercise, high heat, or both, sweating is the body’s way of cooling us down, by absorbing heat and releasing it into the atmosphere. The process of evaporation is key to this function; that’s why doctors say to avoid wiping sweat if you can, letting it dissipate on its own instead. (If you’re dripping, however, you might as well wipe; anything that hits the floor won’t get a chance to cool you down.) But when we’re so used to “sweating it out,” how do we know when hot may be getting a little over the top?

It’s a simple matter of self-awareness, says Devarshi Steven Hartman, Dean of the Kripalu School of Yoga and a fan of hot yoga. “Sweating is detoxifying, while the heat itself can make our bodies more amenable to certain postures,” he says, noting that people with high blood pressure or heart conditions should use extra caution—or, even better, get the okay from a doctor first—when doing yoga in high heat. The downsides, of course, include the risk of dehydration and becoming overly exhausted. “Levels of tolerance are very individual, and can vary day by day,” he says.